The present invention relates to a tool grinding machine, especially for sharpening and regrinding drill bits, end-milling cutters, reamers, etc.
Tool grinding machines for sharpening or regrinding of cutting tools, especially end-milling cutters with spherical cutting heads are nowadays controlled by CNC control. In order to be able to adjust to different geometries of end-mill cutters with spherical cutter heads, the grinding machines need at least five CNC-controlled axes. This is also true for conventional and end-milling cutters and conical end-milling cutters with spherical cutter heads. The known tool grinding machines, in general, have a plurality of grinding wheels which can be moved into a respective grinding position in order to ensure the required flexibility during grinding of differently sized tools and tools of different geometries. In general, different suitable grinding wheels are provided for the different machining steps, such as, for example, spiral groove cutting, grinding of tool ends, regrinding and finish grinding, etc. This plurality of grinding wheels can be arranged adjacent to one another on a single grinding spindle, whereby the grinding wheels must be spaced from one another such that no hinderance during grinding of the tool with one or the other grinding wheels occurs. Instead of a plurality of grinding wheels on one single spindle, it is also possible to arrange a plurality of spindles having one or more grinding wheels thereat whereby the respectively required spindle is then moved into the working or grinding position. A drill bit grinding machine with two grinding wheels and two parallel grinding spindles is disclosed in German Patent 33 48 060 C2. A drill bit grinding machine, having a grinding wheel that is supported on a spindle connected to a horizontally linearly moveable slide on which the drive motor for the grinding spindle is also arranged, is known from German Patent 41 13 146 C2.
In the design having a plurality of grinding wheels on a single grinding spindle, grinding wheels having only a relatively small diameter between 50 and 100 mm can be used in order to avoid too great a distance between the grinding wheels and thus too great a projection of the grinding wheel past the grinding spindle. This is necessary because the danger of hindering one another is greater, the greater the diameter of the grinding wheel when a plurality of grinding wheels is arranged on a grinding spindle, especially when tools with spiral grooves such as end-milling cutters must be machined. Furthermore, for certain grinding machining steps, especially for grinding end-milling cutters with spherical cutter heads, grinding wheels with small diameters are required for grinding the groove within the spherical cutter head while for other machining steps at the same tool larger diameter grinding wheels are much more efficient. However, in order to avoid hinderance between the grinding wheels during grinding, the grinding wheels on a single spindle must be provided with substantially the same diameter.
In a known design with two grinding wheels on two grinding spindles, the grinding spindles are arranged coaxially to one another whereby this axis extends horizontally and the grinding wheels are moveable by rotation about a vertical axis, which extends approximately centrally between the two grinding spindles, can be moved into the machining position at the tool. The axis of rotation about which the grinding spindles with their respective grinding wheels are rotated in order to bring them into the respective working position is always spaced relatively far away from the grinding wheel so that even for a very stiff construction vibrations and indexing imprecisions will occur. The possibility of arranging the spindles at a very stiff support is also impeded by the fact that below the grinding spindle a free space must be available in order not to impede the movement of relatively long tools. For grinding at high output and great material removal rate, the stiffness of such a construction is often not sufficient.
When dressing the grinding wheels, it is necessary in these known tool grinding machines that the grinding wheels must be removed and transported to a separate dressing device in order for them to be machined.
It is therefore an object of the present invention to provide a tool grinding machine with at least two grinding spindles that allows to arrange the axis of the grinding spindles closely adjacent to one another and on a stiff support so that grinding can be performed at great output and at great material removal rate without causing vibrations and with great precision. Furthermore, it should be possible to dress the grinding wheels within the tool grinding machine.